Sulfoxide/glycol ether based solvents for use in the electronics industry

ABSTRACT

Solvents useful for removing, among other things, photoresists and poly(amic acid)/polyimide from display/semiconductor substrates or electronic processing equipment, consist essentially of:
         (A) a first component consisting of a sulfoxide, e.g., DMSO;   (B) a second component consisting of a glycol ether, e.g., ethylene glycol monobutyl ether; and   (C) a third component consisting of at least one of N-formyl morpholine, N,N-dimethyl propionamide, 3-methoxy-N,N-dimethyl propanamide, triethyl phosphate, N,N-dimethyl acetamide; N,N-diethyl acetamide, N,N-diethyl propionamide, N-methyl acetamide, N-methyl propionamide, N-ethyl acetamide, and N-ethyl propionamide.

FIELD

This invention relates to ecology-friendly solvents (“eco-solvents”)useful in the manufacture of various electronic components, e.g.,display units and semiconductors.

BACKGROUND

Some polar solvents, e.g., N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc), dimethyl formamide (DMF), etc., have reproductivetoxicity, which drive the ever increasing global safety and regulatoryconcerns related to these materials. For example, NMP is listed in theSubstance of Very High Concerns (SVHC) registry of the European GloballyHarmonized System of Classification and Labeling of Chemicals (GHS) andREACH Annex XVII which lists the restrictions on the manufacture,placing on the market and use of certain dangerous substances, mixturesand articles.

NMP is used in the electronics industry for cleaning and stripping ofvarious parts (e.g., components for display units, semiconductorsubstrates, etc.) and equipment, and considerable amounts of it areconsumed annually. Developing an eco-solvent to achieve similarperformance with a better environmental profile than NMP is an urgentrequest from electronic processing customers. This invention detailssolvent combinations that, in some embodiments, provide the same orbetter cleaning ability, and stripping ability for photoresist removal,than NMP.

SUMMARY

In one embodiment the invention is a solvent consisting essentially of:

and

-   -   (A) a first component consisting of a sulfoxide;    -   (B) a second component consisting of a glycol ether; and    -   (C) a third component consisting of at least one of N-formyl        morpholine, N,N-dimethyl propionamide, 3-methoxy-N,N-dimethyl        propanamide, triethyl phosphate, N,N-dimethyl acetamide;        N,N-diethyl acetamide, N,N-diethyl propionamide, N-methyl        acetamide, N-methyl propionamide, N-ethyl acetamide, and N-ethyl        propionamide.

In one embodiment the invention is a process for cleaning or strippingthe surface of a substrate, the process comprising the step ofcontacting the substrate with a solvent consisting essentially of:

-   -   (A) a first component consisting of a sulfoxide;    -   (B) a second component consisting of a glycol ether; and    -   (C) a third component consisting of at least one of N-formyl        morpholine, N,N-dimethyl propionamide, 3-methoxy-N,N-dimethyl        propanamide, triethyl phosphate, N,N-dimethyl acetamide;        N,N-diethyl acetamide, N,N-diethyl propionamide, N-methyl        acetamide, N-methyl propionamide, N-ethyl acetamide, and N-ethyl        propionamide.

DETAILED DESCRIPTION Definitions

For purposes of United States patent practice, the contents of anyreferenced patent, patent application or publication are incorporated byreference in their entirety (or its equivalent U.S. version is soincorporated by reference) especially with respect to the disclosure ofdefinitions (to the extent not inconsistent with any definitionsspecifically provided in this disclosure) and general knowledge in theart.

The numerical ranges disclosed herein include all values from, andincluding, the lower and upper value. For ranges containing explicitvalues (e.g., 1 to 7), any subrange between any two explicit values isincluded (e.g., 1 to 2; 2 to 6; 5 to 7; 3 to 7; 5 to 6; etc.).

The terms “comprising,” “including,” “having,” and their derivatives,are not intended to exclude the presence of any additional component,step or procedure, whether or not the same is specifically disclosed. Inorder to avoid any doubt, all compositions claimed through use of theterm “comprising” may include any additional additive, adjuvant, orcompound, whether polymeric or otherwise, unless stated to the contrary.In contrast, the term, “consisting essentially of” excludes from thescope of any succeeding recitation any other component, step, orprocedure, excepting those that are not essential to operability. Theterm “consisting of” excludes any component, step, or procedure notspecifically delineated or listed. The term “or,” unless statedotherwise, refers to the listed members individually as well as in anycombination. Use of the singular includes use of the plural and viceversa.

Unless stated to the contrary, implicit from the context, or customaryin the art, all parts and percents are based on weight and all testmethods are current as of the filing date of this disclosure.

“Solvent” and like terms mean a substance that is capable of dissolvinganother substance (i.e., a solute) to form an essentially uniformlydispersed mixture (i.e., solution) at the molecular or ionic size level.

“Electronic part” and like terms mean an in-process or finished product,or component of a product, of a manufacturing process for electronicgoods, such as a semiconductor or display unit. Electronic part, as usedin the context of this invention, includes the equipment used tomanufacture the product.

“In-process product” and like terms mean an unfinished or intermediateproduct. In-process products include starting materials, e.g., materialsas received from vendors, or materials before subjected to the start ofthe manufacturing process.

“Photoresist” and like terms mean a photosensitive resin that loses itsresistance to chemical etching when exposed to radiation and is usedespecially in the transference of a circuit pattern to a semiconductorchip during the production of an integrated circuit.

“Cleaning” and like terms mean, in the context of this invention, theremoval of particulate contamination and metal ions from the surface ofa substrate, usually from the surface of an in-process electronic partto ready the part for subsequent processing.

“Stripping” and like terms mean, in the context of this invention, theremoval of a layer, e.g., coating or film, from the surface of asubstrate, such as the removal of a photoresist from the surface of asemiconductor substrate.

“Freezing point” and like terms mean the temperature at which a liquidchanges into a solid. The freezing point of the solvents of thisinvention can be determined by using test equipment that includes aglass container, cooling bath or cooling trap or refrigerator withtemperature control system, and thermometer or thermal sensor. A twentygram (20 g) sample of liquid solvent is placed in a glass container,e.g., a glass cylinder. The temperature of the cooling bath or coolingtrap or refrigerator is set at 0° C. A thermometer or thermal sensor isused to determine the temperature of cold liquid or cold airflow insideof cooling bath or cooling trap or refrigerator. The glass containerwith prepared solvent sample is stored in the cooling bath or coolingtrap for at least 12 hours. The freezing point of the solvent sample isdetermined by observing its physical state, i.e., liquid or solid. Ifthe solvent sample still shows fluidity, the current setting temperatureof the cooling bath or cooling trap or refrigerator is reduced until itstemperature determined by thermometer or thermal sensor is 1° C. lessthan its previous temperature. The procedure is repeated until thesolvent sample is solid.

Poly(amic acid) is an intermediate polymer in the synthesis ofpolyimide. It is soluble in polar solvents due to strong hydrogenbonding.

Polyimide (PI) is a polymer of imide monomers. It is normally producedby the reaction of a dianhydride and a diamine. One common PI used inthe electronics industry is KAPTON™ It is produced from the condensationof pyromellitic dianhydride and 4,4′-oxydiphenylamine.

Solvents

The solvents of this invention consist essentially of a first component,a second component, and a third component. The first component consistsof, or is, a sulfoxide. The second component consists of, or is, aglycol ether. The third component consists of, or consists essentiallyof, at least one of N-formyl morpholine (CAS Number 4394-85-8),N,N-dimethyl propionamide (CAS Number 758-96-3), 3-methoxy-N,N-dimethylpropanamide (CAS Number 53185-52-7), triethyl phosphate (CAS Number78-40-0), N,N-dimethyl acetamide (CAS Number 127-19-5); N,N-diethylacetamide (CAS Number 685-91-6), N,N-diethyl propionamide (CAS Number1114-51-8), N-methyl acetamide (CAS Number 79-16-3), N-methylpropionamide (CAS Number 1187-58-2), N-ethyl acetamide (CAS Number625-50-3), and N-ethyl propionamide (CAS Number 5129-72-6). The first,second and third components form a blend, and the blend may or may notbe phase separated. In one embodiment the solvent has a freezing pointof less than −25° C.

Sulfoxides

The first component of the solvent of this invention consists of, or is,a sulfoxide, i.e., a compound containing a sulfinyl functional groupattached to two carbon atoms. It is a polar functional group. Sulfoxidesare the oxidized derivatives of sulfides. Representative sulfoxidesinclude, but are not limited to, diethyl sulfoxide, butyl sulfoxide,tetramethylene sulfoxide and dimethyl sulfoxide (DMSO). The firstcomponent can consist of one or more sulfoxides. In one embodiment thefirst component consists of one sulfoxide. In one embodiment the firstcomponent consists of two or more sulfoxides. In one embodiment thefirst component consists of, or is, DMSO (CAS Number 67-68-5).

Glycol Ethers

The second component of the solvent of this invention consists of, oris, a glycol ether, i.e., a compound based on an alkyl ether of ethyleneglycol or propylene glycol. These solvents typically have a higherboiling point, together with the favorable solvent properties oflower-molecular weight ethers and alcohols. Representative glycol ethersinclude, but are not limited to, ethylene glycol monobutyl ether,ethylene glycol monopropyl ether, diethylene glycol monoethyl ether,propylene glycol monomethyl ether, dipropylene glycol monomethyl ether,and tripropylene glycol monomethyl ether. The second component canconsist of one or more glycol ethers. In one embodiment the secondcomponent consists of one glycol ether. In one embodiment the secondcomponent consists of two or more glycol ethers. In one embodiment thesecond component is an ethylene glycol alkyl ether. In one embodimentthe second component is a propylene glycol alkyl ether. In oneembodiment the alkyl component of the ethylene or propylene glycol etheris an alkyl group of 2 to 12, or 3 to 10, or 3 to 8, carbon atoms. Inone embodiment the second component consists of, or is, ethylene glycolmonobutyl ether (CAS Number 111-76-2).

Embodiments

In one embodiment the solvent is a blend consisting of, or consistingessentially of, a sulfoxide as the first component, a glycol ether asthe second component, and N-formyl morpholine as the third component.

In one embodiment the solvent is a blend consisting of, or consistingessentially of, a sulfoxide as the first component, a glycol ether asthe second component, and N,N-dimethyl propionamide as the thirdcomponent.

In one embodiment the solvent is a blend consisting of, or consistingessentially of, a sulfoxide as the first component, a glycol ether asthe second component, and 3-methoxy-N,N-dimethyl propanamide as thethird component.

In one embodiment the solvent is a blend consisting of, or consistingessentially of, a sulfoxide as the first component, a glycol ether asthe second component, and triethyl phosphate as the third component.

In one embodiment the solvent is a blend consisting of, or consistingessentially of, DMSO as the first component, a glycol ether as thesecond component, and N-formyl morpholine as the third component.

In one embodiment the solvent is a blend consisting of, or consistingessentially of, DMSO as the first component, a glycol ether as thesecond component, and N,N-dimethyl propionamide as the third component.

In one embodiment the solvent is a blend consisting of, or consistingessentially of, DMSO as the first component, a glycol ether as thesecond component, and 3-methoxy-N,N-dimethyl propanamide as the thirdcomponent.

In one embodiment the solvent is a blend consisting of, or consistingessentially of, DMSO as the first component, a glycol ether as thesecond component, and triethyl phosphate as the third component.

In one embodiment the solvent is a blend consisting of, or consistingessentially of, a sulfoxide as the first component, ethylene glycolmonobutyl ether as the second component, and N-formyl morpholine as thethird component.

In one embodiment the solvent is a blend consisting of, or consistingessentially of, a sulfoxide as the first component, ethylene glycolmonobutyl ether as the second component, and N,N-dimethyl propionamideas the third component.

In one embodiment the solvent is a blend consisting of, or consistingessentially of, a sulfoxide as the first component, ethylene glycolmonobutyl ether as the second component, and 3-methoxy-N,N-dimethylpropanamide as the third component.

In one embodiment the solvent is a blend consisting of, or consistingessentially of, a sulfoxide as the first component, ethylene glycolmonobutyl ether as the second component, and triethyl phosphate as thethird component.

In one embodiment the solvent is a tertiary blend consisting of, orconsisting essentially of, DMSO as the first component, ethylene glycolmonobutyl ether as the second component, and N-formyl morpholine as thethird component.

In one embodiment the solvent is a tertiary blend consisting of, orconsisting essentially of, DMSO as the first component, ethylene glycolmonobutyl ether as the second component, and N,N-dimethyl propionamideas the third component.

In one embodiment the solvent is a tertiary blend consisting of, orconsisting essentially of, DMSO as the first component, ethylene glycolmonobutyl ether as the second component, and 3-methoxy-N,N-dimethylpropanamide as the third component.

In one embodiment the solvent is a tertiary blend consisting of, orconsisting essentially, of DMSO as the first component, ethylene glycolmonobutyl ether as the second component, and triethyl phosphate as thethird component.

In one embodiment the solvent is a quaternary blend consisting of, orconsisting essentially of, DMSO as the first component, ethylene glycolmonobutyl ether as the second component, and a combination of N-formylmorpholine and N,N-dimethyl propionamide as the third component.

In one embodiment the solvent is a quaternary blend consisting of, orconsisting essentially of, DMSO as the first component, ethylene glycolmonobutyl ether as the second component, and a combination of N-formylmorpholine and 3-methoxy-N,N-dimethyl propanamide as the thirdcomponent.

In one embodiment the solvent is a quaternary blend consisting of, orconsisting essentially of, DMSO as the first component, ethylene glycolmonobutyl ether as the second component, and a combination of N-formylmorpholine and triethyl phosphate as the third component.

In one embodiment the solvent is a quaternary blend consisting of, orconsisting essentially of, DMSO as the first component, ethylene glycolmonobutyl ether as the second component, and a combination ofN,N-dimethyl propionamide and 3-methoxy-N,N-dimethyl propanamide as thethird component.

In one embodiment the solvent is a quaternary blend consisting of, orconsisting essentially of, DMSO as the first component, ethylene glycolmonobutyl ether as the second component, and a combination ofN,N-dimethyl propionamide and triethyl phosphate as the third component.

In one embodiment the solvent is a quinary blend consisting of, orconsisting essentially of, DMSO as the first component, ethylene glycolmonobutyl ether as the second component, and a combination of N-formylmorpholine, N,N-dimethyl propionamide and 3-methoxy-N,N-dimethylpropanamide as the third component.

In one embodiment the solvent is a quinary blend consisting of, orconsisting essentially of, DMSO as the first component, ethylene glycolmonobutyl ether as the second component, and a combination of N-formylmorpholine, N,N-dimethyl propionamide and triethyl phosphate as thethird component.

In one embodiment the solvent is a quinary blend consisting of, orconsisting essentially of, DMSO as the first component, ethylene glycolmonobutyl ether as the second component, and a combination ofN,N-dimethyl propionamide, 3-methoxy-N,N-dimethyl propanamide andtriethyl phosphate as the third component.

In one embodiment the solvent is a senary blend consisting of, orconsisting essentially of, DMSO as the first component, ethylene glycolmonobutyl ether as the second component, and a combination of N-formylmorpholine, N,N-dimethyl propionamide, 3-methoxy-N,N-dimethylpropanamide and triethyl phosphate as the third component.

In one embodiment the solvent consists of, or consists essentially of,in weight percent (wt %) based on the weight of the solvent, from 50 to90 wt % of the first component, from 9 to 40 wt % of the secondcomponent, and from 1 to 30 wt % of the third component.

In one embodiment the solvent consists of, or consists essentially of,in weight percent (wt %) based on the weight of the solvent, from 50 to90 wt % of DMSO, from 9 to 40 wt % of ethylene glycol monobutyl ether,and from 1 to 30 wt % of at least one of N-formyl morpholine,N,N-dimethyl propionamide, 3-methoxy-N,N-dimethyl propanamide andtriethyl phosphate as the third component.

In one embodiment the solvent consists of, or consists essentially of,in weight percent (wt %) based on the weight of the solvent, from 10 to30 wt % of the first component, from 1 to 30 wt % of the secondcomponent, and from 70 to 90 wt % of the third component.

In one embodiment the solvent consists of, or consists essentially of,in weight percent (wt %) based on the weight of the solvent, from 10 to30 wt % of DMSO, from 10 to 30 wt % of ethylene glycol monobutyl ether,and from 70 to 90 wt % of at least one of N-formyl morpholine,N,N-dimethyl propionamide, 3-methoxy-N,N-dimethyl propanamide, triethylphosphate, N,N-dimethyl acetamide; N,N-diethyl acetamide, N,N-diethylpropionamide, N-methyl acetamide, N-methyl propionamide, N-ethylacetamide, and N-ethyl propionamide as the third component.

In one embodiment the solvent consists of, or consists essentially of,in weight percent (wt %) based on the weight of the solvent, from 10 to30 wt % of DMSO, from 10 to 30 wt % of ethylene glycol monobutyl ether,and from 70 to 90 wt % of N,N-dimethyl propionamide, as the thirdcomponent.

In one embodiment the solvent has a freezing point of less than (<)−25°C., or <−20° C., or <−15° C., or <−10° C. In one embodiment the solventhas a freezing point from −25° C. or less to −10° C. or more.

In those embodiments in which the third component consists of more thanone substance, e.g., the third component consists essentially ofN-formyl morpholine and N,N-dimethyl propionamide and/or3-methoxy-N,N-dimethyl propanamide and/or triethyl phosphate, etc., theamount of each compound in the third component can vary widely and toconvenience. The amount of each individual substance in the thirdcomponent can vary from 0 to 100 wt %, or from 1 to 99 wt %, or from 10to 90 wt %, or from 20 to 80 wt % or from 30 to 70 wt %, or from 40 to60 wt %, or 50 wt %, based on the weight of the component.

Optional materials that are not essential to the operability of, but canbe included in, the solvents of this invention include, but are notlimited to, antioxidants, colorants, water scavengers, stabilizers, andthe like. These materials do not have any material impact on theefficacy of the solvent for cleaning or stripping electronic parts.These optional materials are used in known amounts, e.g., 0.10 to 5, or4, or 3, or 2, or 1, weight percent based on the weight of the solvent,and they are used in known ways.

Preparation of the Solvent

The solvents of this invention are made using known equipment and knowntechniques. The individual components of the solvent are commerciallyavailable, liquid at ambient conditions (23° C. and atmosphericpressure), and can simply be mixed with one another using conventionalmixing equipment and standard blending protocols. The components can beadded to one another in any order including simultaneously.

Use of the Solvents

The solvents of this invention are eco-solvents, i.e., they do not have,or have at a reduced level, the toxicology issues associated with NMP.These solvents are useful for cleaning and/or stripping the surfaces ofsubstrates of contaminants and other unwanted substances, particularlypolar contaminants and polar unwanted substances.

In one embodiment the solvents of this invention are intended as areplacement for NMP and other polar solvents used in the electronicsindustry. As such, they are used in the same manner as NMP and the otherpolar solvents in such operations as cleaning and stripping ofelectronic parts and equipment, and the removal of photoresists fromvarious substrates, e.g., semiconductor substrates, and the removal ofpolyamic acid polymer residue from polyimide coating equipment, e.g.,alignment layer and flexible display substrate coating machine.Typically, these methods or processes include the step of contacting theobject or substrate to be cleaned or stripped, or from which aphotoresist or a polyamic acid/polyimide residue is to be removed, withthe solvent under any of various conditions, e.g., ambient conditions,or at an elevated or reduced temperature, with or without flow oragitation, e.g., printing, spinning, immersing, flushing, vibrating,showering, spraying, etc., for a sufficient period of time to dissolvewhatever material, e.g., a contaminant such as poly(amic acid)/polyimideresidue, dianhydride, diamine, etc.; a photoresist, and the like, thatis to be removed. This contacting step is then typically followed byrinse (one or more, typically with an aqueous liquid such as deionizedwater) and drying steps. Solvents with a freezing temperature of lessthan −25° C. can be particularly favored for use in the processes ofcleaning and/or stripping electronic parts and equipment.

The following examples are nonlimiting illustrations of the invention.

EXAMPLES

Materials

Poly(amic acid), precursor of polyimide: poly (pyromelliticdianhydride-co-4,4′-oxydianiline), amic acid (from Sigma-Aldrich, 15˜16wt % dissolved in NMP).

Photoresist: SFP-1400 (from Merck).

Solvents: N-formyl morpholine (from Accela ChemBio, 98%), dimethylsulfoxide (DMSO) (from Sinopharm, 99%), triethyl phosphate (fromSinopharm, 99%), 3-methoxy-N,N-dimethyl propanamide (from BOC Science,98%), N,N-dimethyl propionamide (from Energy Chemical, 98%), andethylene glycol monobutyl ether (from The Dow Chemical Company, 99%).

Solvents

The solvents are designed according to Hansen Solubility Parameter ofNMP, DMF, 3-methoxy-N,N-dimethyl propanamide, etc. These commercializedsolvents have strong dissolution ability for most electronic materials.The solvents are described in Table 1.

TABLE 1 Solvents Component A Weight % Component B Weight % Component CWeight % Example 1 dimethyl 64 ethylene glycol 30 N-formyl 6 sulfoxidemonobutyl ether morpholine 2 dimethyl 58 ethylene glycol 30 N-formyl 12sulfoxide monobutyl ether morpholine 3 dimethyl 52 ethylene glycol 30N-formyl 18 sulfoxide monobutyl ether morpholine 4 dimethyl 65 ethyleneglycol 28 N,N-dimethyl 7 sulfoxide monobutyl ether propionamide 5dimethyl 65 ethylene glycol 20 N,N-dimethyl 15 sulfoxide monobutyl etherpropionamide 6 dimethyl 66 ethylene glycol 25 3-methoxy- 7 sulfoxidemonobutyl ether N,N-dimethyl propanamide 7 dimethyl 60 ethylene glycol25 3-methoxy- 15 sulfoxide monobutyl ether N,N-dimethyl propanamide 8dimethyl 65 ethylene glycol 29 triethyl 6 sulfoxide monobutyl etherphosphate 9 dimethyl 65 ethylene glycol 23 triethyl 12 sulfoxidemonobutyl ether phosphate 10  dimethyl 65 ethylene glycol 17 triethyl 18sulfoxide monobutyl ether phosphate Comparative Example 1 N-methyl-2-100 pyrrolidone 2 3-methoxy-N,N- 100 dimethyl propanamide 3monoethanolamine 15 diethylene 20 DI water 65 glycol butyl ether 4monoethanolamine 30 diethylene 70 glycol butyl ether 5 monoethanolamine10 N-methyl-2- 70 DI water 20 pyrrolidone

Protocols for Examples 1-10 and Comparative Examples 1-5

Poly(amic acid) dissolution: A solution of poly (pyromelliticdianhydride-co-4,4′-oxydianiline), amic acid precursor in NMP iscontacted with deionized (DI) water or other NMP-insoluble liquid toextract the precursor from the NMP. The poly(amic acid) precursor isthen baked at 54° C. for 4 hours to evaporate any residualsolvent/liquid before it is dissolved by contact with the test solvent.Results are recorded after 12 hours at 54° C.

Photoresist stripping: Place 2 milliliters (ml) SFP-1400 photoresistsolution onto the surface of glass substrate with a size of 100millimeters (mm)×100 mm×1 mm. The substrate is spun with a rotationspeed of 500 revolutions per minute (rpm) for 10 seconds (s) to spreadout the photoresist solution. The rotation speed is then accelerated to1000 rpm for 30 s to coat the photoresist homogenously and spin outredundant solvent. The coated substrate is heated to evaporate solventat 130° C. for 10 minutes (min). The stripping step prepares 30 grams(g) example in the container. The baked substrate is placed into thecontainer with shaking, and finally the time is measured for completelyremoving photoresist from the substrate.

Results

Poly(amic acid) dissolution: The poly (pyromelliticdianhydride-co-4,4′-oxydianiline), amic acid solubility results of eachproduct are reported in Table 2. The content of polymer in each exampleand comparative sample is 20% by weight. The performance is judgedthrough the fluidity of the solution. The two examples, N-formylmorpholine/N,N-dimethyl propionamide, and dimethylsulfoxide/N,N-dimethyl propionamide exhibit good fluidity with lowviscosity. N-formyl morpholine/3-methoxy-N,N-dimethyl propanamide showsa certain fluidity and suitable viscosity. However, in comparativesamples, 3-methoxy-N,N-dimethyl propanamide, gels occur in thesolutions, which represents the oversaturation of polymer. ForN-methyl-2-pyrrolidone, although the sample is able to flow, itsviscosity is comparatively high. In general, the solubility of poly(pyromellitic dianhydride-co-4,4′-oxydianiline), amic acid inN-methyl-2-pyrrolidone should be 15% by weight for commercial products.For 3-methoxy-N,N-dimethyl propanamide, the related solubility iscomparatively lower. Therefore, the solvency for poly(amic acid) ofexamples is better than comparative samples.

TABLE 2 Poly(amic acid) (poly (pyromelliticdianhydride-co-4,4′-oxydianiline), amic acid) Solvency Performance ofSolvents Example Component A Weight % Component B Weight % Component CWeight % Performance dimethyl 64 ethylene glycol 30 N-formyl 6 ◯sulfoxide monobutyl ether morpholine dimethyl 58 ethylene glycol 30N-formyl 12 ◯ sulfoxide monobutyl ether morpholine dimethyl 52 ethyleneglycol 30 N-formyl 18 ◯ sulfoxide monobutyl ether morpholine dimethyl 65ethylene glycol 28 N,N-dimethyl 7 ◯ sulfoxide monobutyl etherpropionamide dimethyl 65 ethylene glycol 20 N,N-dimethyl 15 ◯ sulfoxidemonobutyl ether propionamide dimethyl 66 ethylene glycol 253-methoxy-N,N- 7 ◯ sulfoxide monobutyl ether dimethyl propanamidedimethyl 60 ethylene glycol 25 3-methoxy-N,N- 15 ◯ sulfoxide monobutylether dimethyl propanamide dimethyl 65 ethylene glycol 29 triethylphosphate 6 ◯ sulfoxide monobutyl ether dimethyl 65 ethylene glycol 23triethyl phosphate 12 ◯ sulfoxide monobutyl ether dimethyl 65 ethyleneglycol 17 triethyl phosphate 18 ◯ sulfoxide monobutyl ether ComparativeComponent Weight % Performance N-methyl-2-pyrrolidone 100 ◯3-methoxy-N,N-dimethyl 100 X propanamide Open circle = fluidity; X =high viscosity (no flow)

Photoresist stripping: The photoresist stripping results of eachcombination are listed in Table 3. The performance is evaluated bystripping time. The example, dimethyl sulfoxide/ethylene glycolmonobutyl ether/N,N-dimethyl propionamide can completely strip thecoated photoresist from the glass substrate within 15 seconds. The otherinvented dimethyl sulfoxide/ethylene glycol monobutyl ether basedexamples require 15 to 20 seconds to strip the photoresist. Water basedmonoethanolamine/diethylene glycol butyl ether andmonoethanolamine/N-methyl-2-pyrrolidone comparative samples Dongji(KR1403516B1) need almost a half-minute for stripping. However the othercommercial combination, monoethanolamine/diethylene glycol butyl etherwithout water content shows relatively slow stripping speed. Therefore,the examples possess better stripping performance on SFP-1400photoresist.

TABLE 3 Photoresist (SFP-1400) Stripping Performance of SolventsComponent A Weight % Component B Weight % Component C Weight %Performance Example dimethyl 64 ethylene 30 N-formyl 6 ◯ sulfoxideglycol morpholine monobutyl ether dimethyl 58 ethylene 30 N-formyl 12 ◯sulfoxide glycol morpholine monobutyl ether dimethyl 52 ethylene 30N-formyl 18 ◯ sulfoxide glycol morpholine monobutyl ether dimethyl 65ethylene 28 N,N-dimethyl 7 ⊙ sulfoxide glycol propionamide monobutylether dimethyl 65 ethylene 20 N,N-dimethyl 15 ⊙ sulfoxide glycolpropionamide monobutyl ether dimethyl 66 ethylene 25 3-methoxy- 7 ◯sulfoxide glycol N,N-dimethyl monobutyl propanamide ether dimethyl 60ethylene 25 3-methoxy- 15 ◯ sulfoxide glycol N,N-dimethyl monobutylpropanamide ether dimethyl 65 ethylene 29 triethyl 6 ◯ sulfoxide glycolphosphate monobutyl ether dimethyl 65 ethylene 23 triethyl 12 ◯sulfoxide glycol phosphate monobutyl ether dimethyl 65 ethylene 17triethyl 18 ◯ sulfoxide glycol phosphate monobutyl ether Comparativemonoethanolamine 15 diethylene 20 DI water 65 Δ glycol butyl ethermonoethanolamine 30 diethylene 70 X glycol butyl ether monoethanolamine10 N-methyl-2- 70 DI water 20 Δ pyrrolidone Circle with a dot = lessthan (<) 15 seconds; Open circle (i.e., circle without dot) = 15020seconds; Triangle - 20-30 seconds; and X = greater than or equal to (≥)30 seconds.

Protocols for Examples 11-17 and Comparative Examples 6-10

The solvents are designed to have a freezing point lower than −25° C.,and faster photoresist stripping and polyamic acid dissolution than NMP.For each blending example, The detailed ratio for each inventive andcomparative example is reported in the Table 4.

TABLE 4 Solvents Component A Weight % Component B Weight % Component CWeight % Example 11 dimethyl 20 ethylene glycol 20 N,N-dimethyl 60sulfoxide monobutyl propionamide ether 12 dimethyl 10 ethylene glycol 20N,N-dimethyl 70 sulfoxide monobutyl propionamide ether 13 dimethyl 20ethylene glycol 30 N,N-dimethyl 50 sulfoxide monobutyl propionamideether 14 dimethyl 10 ethylene glycol 30 N,N-dimethyl 60 sulfoxidemonobutyl propionamide ether 15 dimethyl 30 ethylene glycol 40N,N-dimethyl 30 sulfoxide monobutyl propionamide ether 16 dimethyl 20ethylene glycol 40 N,N-dimethyl 40 sulfoxide monobutyl propionamideether 17 dimethyl 10 ethylene glycol 40 N,N-dimethyl 50 sulfoxidemonobutyl propionamide ether Comparative Example  6 N-methyl-2- 100pyrrolidone  7 3-methoxy-N,N- 100 dimethyl propanamide  8monoethanolamine 15 diethylene 20 DI water 65 glycol butyl ether  9monoethanolamine 30 diethylene 70 glycol butyl ether 10 monoethanolamine10 N-methyl-2- 70 DI water 20 pyrrolidone

Polyamic Acid Dissolution

The procedure of Examples 1-10 and Comparative Examples 1-5 is repeatedhere.

Photoresist Stripping

The procedure of Examples 1-10 and Comparative Examples 1-5 is repeatedhere.

Freeze Testing

Twenty gram (20 g) samples are prepared and stored in a refrigerator at−25° C. for 24 hours after which the samples are viewed for liquid orsolid (frozen) state.

Results

Polymeric Acid Dissolution

The poly (pyromellitic dianhydride-co-4,4′-oxydianiline), amic acidsolubility results of each product are reported in Table 5. The amountof polymer in each example and comparative sample is 30% by weight. Theperformance is judged through the viscosity of the solution. Alldimethyl sulfoxide/ethylene glycol monobutyl ether based solvents cancompletely dissolve polyamic acid and exhibit good viscosity, whichindicates the invented combinations have equivalent performance withN-methyl-2-pyrrolidone. As for the other comparative sample,3-methoxy-N,N-dimethyl propanamide, the related solubility iscomparatively lower. The solution is hard to flow. Therefore, thesolvency for polyamic acid of the inventive examples is good relative tocertain commercial products.

TABLE 5 Polyamic Acid Solvency Performance of Various Solvents ExampleComponent A Weight % Component B Weight % Component C Weight %Performance dimethyl 20 ethylene 20 N,N-dimethyl 60 ◯ sulfoxide glycolpropionamide monobutyl ether dimethyl 10 ethylene 20 N,N-dimethyl 70 ◯sulfoxide glycol propionamide monobutyl ether dimethyl 20 ethylene 30N,N-dimethyl 50 ◯ sulfoxide glycol propionamide monobutyl ether dimethyl10 ethylene 30 N,N-dimethyl 60 ◯ sulfoxide glycol propionamide monobutylether Comparative Component Weight % Performance N-methyl-2-pyrrolidone100 ◯ 3-methoxy-N,N-dimethyl 100 X propanamide ◯ = Low Viscosity X =High Viscosity

Photoresist Stripping

The photoresist stripping results of each combination are reported inTable 6. The performance is evaluated by stripping time. Dimethylsulfoxide/ethylene glycol monobutyl ester/N,N-dimethyl propionamide cancompletely strip the coated photoresist from the glass substrate within15 seconds. The dimethyl sulfoxide/ethylene glycol monobutyl ester basedexamples require 15 to 20 seconds to strip the photoresist. Water-basedmonoethanolamine/diethylene glycol butyl ether andmonoethanolamine/N-methyl-2-pyrrolidone comparative samples requiredclose to a half minute for stripping. However the other commercialcombination, monoethanolamine/diethylene glycol butyl ether withoutwater content shows relatively slow stripping speed. Therefore, theexamples possess better stripping performance on SFP-1400 photoresist.

TABLE 6 Photoresist Stripping Performance of the Solvents Component AWeight % Component B Weight % Component C Weight % Performance Exampledimethyl 20 ethylene 20 N-formyl 60 ◯ sulfoxide glycol morpholinemonobutyl ether dimethyl 10 ethylene 20 N-formyl 70 ◯ sulfoxide glycolmorpholine monobutyl ether dimethyl 20 ethylene 30 N-formyl 50 ◯sulfoxide glycol morpholine monobutyl ether dimethyl 10 ethylene 30N,N-dimethyl 60 ◯ sulfoxide glycol propionamide monobutyl ether dimethyl30 ethylene 40 N,N-dimethyl 30 ◯ sulfoxide glycol propionamide monobutylether dimethyl 20 ethylene 40 3-methoxy- 40 ◯ sulfoxide glycolN,N-dimethyl monobutyl propanamide ether dimethyl 10 ethylene 403-methoxy- 50 ◯ sulfoxide glycol N,N-dimethyl monobutyl propanamideether Comparative monoethanolamine 15 diethylene 20 DI water 65 Δ glycolbutyl ether monoethanolamine 30 diethylene 70 X glycol butyl ethermonoethanolamine 10 N-methyl-2- 70 DI water 20 Δ pyrrolidone ◯ means <20seconds Δ means 20 to 30 seconds X means >30 seconds

Photoresist Stripping (Frozen)

Twenty gram (20 g) solvent samples are placed into fifty milliliter (50mL) glass cylinders. The solvent-containing glass containers and athermometer are placed into a refrigerator, and the temperature of therefrigerator is set to −25° C. The samples are kept in the refrigeratorat −25° C. for 12 hours. The results are reported in Table 7. Thephysical state of the solvent, i.e., liquid or solid, is determined byvisual inspection of the sample in the glass cylinder. All inventivesamples are liquid. Among the comparative examples,3-methoxy-N,N-dimethyl propanamide and monoethanolamine/diethyleneglycol butyl ether are liquid. However, N-methyl-2-pyrrolidone,monoethanolamine/diethylene glycol butyl ether/DI water andmonoethanolamine/N-methyl-2-pyrrolidone/DI water are solid.

TABLE 7 Liquid/Solid Status of Solvents are −25° C. Component A Weight %Component B Weight % Component C Weight % Performance Example dimethyl20 ethylene 20 N-formyl 60 ◯ sulfoxide glycol morpholine monobutyl etherdimethyl 10 ethylene 20 N-formyl 70 ◯ sulfoxide glycol morpholinemonobutyl ether dimethyl 20 ethylene 30 N-formyl 50 ◯ sulfoxide glycolmorpholine monobutyl ether dimethyl 10 ethylene 30 N,N-dimethyl 60 ◯sulfoxide glycol propionamide monobutyl ether dimethyl 30 ethylene 40N,N-dimethyl 30 ◯ sulfoxide glycol propionamide monobutyl ether dimethyl20 ethylene 40 3-methoxy- 40 ◯ sulfoxide glycol N,N-dimethyl monobutylpropanamide ether dimethyl 10 ethylene 40 3-methoxy- 50 ◯ sulfoxideglycol N,N-dimethyl monobutyl propanamide ether Comparative N-methyl-2-100 X pyrrolidone 3-methoxy-N,N- 100 ◯ dimethyl propanamidemonoethanolamine 15 diethylene 20 DI water 65 X glycol butyl ethermonoethanolamine 30 diethylene 70 ◯ glycol butyl ether monoethanolamine10 N-methyl-2- 70 DI water 20 X pyrrolidone ◯ = Liquid X = Frozen(Solid)

What is claimed is:
 1. A solvent consisting essentially of: (A) from 50to 90 wt% of a first component consisting of a sulfoxide; (B) from 9 to40 wt% of a second component consisting of a glycol ether; and (C) from1 to 30 wt% of 3-methoxy-N,N-dimethyl propanamide, wherein wt % is basedon the weight of the solvent.
 2. The solvent of claim 1 wherein thesulfoxide is DMSO.
 3. The solvent of claim 1 wherein the glycol ether isethylene glycol monobutyl ether.
 4. The solvent of claim 1 wherein thefirst component is DMSO and the second component is ethylene glycolmonobutyl ether.